Multi-plate brakes and clutches are commonly used in vehicles with high torque requirements in vehicle braking applications and/or in power transfer applications. They usually comprise relatively similar components in the form of a carrier (also known as a hub) and a plurality of annular friction plates mounted to the carrier. External splines may be disposed around the periphery of the carrier and may engage with internal splines disposed about the inner edge of the friction plates. Annular reaction plates (also known as spacer plates) may be located in between adjacent friction plates and are mounted to an outer ring, which locates around the plates and carrier. The carrier may be provided with splines and the reaction plates and friction plates may slide on these splines along an axis of rotation of the carrier and/or outer ring. An actuator may be provided to move the reaction and friction plates towards one another.
In the case of a vehicle braking application, the carrier is usually rotatable and the outer ring is fixed. Therefore, the friction plates may rotate with the carrier whilst the reaction plates are fixed. When the friction plates and reaction plates are brought together (i.e. by the actuator), a frictional braking force may be provided that opposes the rotation force of the carrier.
In the case of a power transfer application using a clutch, the carrier and outer ring can both rotate such that the reaction plates rotate with the carrier and the friction plates rotate with the outer ring. When the friction plates and the reaction plates are brought together (i.e. by the actuator), a frictional force may be provided between the friction and reaction plates that will result in the carrier and outer ring rotating substantially together. The clutch therefore acts to transmit a torque between the carrier and outer ring.
Lubricating or cooling fluid, such as oil, may be supplied to the friction and reaction plates. Arrangements which apply such lubrication are commonly known as “wet running” multi-plate brakes or clutches. In addition to cooling and lubricating the plates, the fluid may assist in providing the frictional force between the reaction and friction plates. The fluid may form a film on the surfaces of the plates which prevents direct contact between the plates. The forces generated within the film may provide a resistance to rotation between the plates and thus provide the required frictional force. The avoidance of direct contact between the plates may result in reduced wear and thus prolong the life of the clutch or brake.
Various different arrangements of multi-plate brakes and clutches have previously been developed in attempts to provide sufficient fluid to the plates. For example, as is disclosed in US-A-2009/0194384 or U.S. Pat. No. 7,383,932, a number of holes may be provided through the carrier either in each spline or in the gaps in the carrier between each spline. The fluid is injected into the carrier and as the carrier rotates centrifugal forces direct the fluid through the holes in a direct path towards the plates.
However, the flow of fluid from such holes can only be directed to the plates that are directly adjacent to the holes. Therefore, the coolest fluid will only ever contact those plates directly adjacent to the holes. In addition, the fluid flow path to the plates furthest from the holes can be disrupted by the internal or external splines. As a result, there can be an uneven distribution of the fluid throughout the plates.